1. Field of the Invention
The present invention concerns a compressor with recycling of a secondary flow.
More precisely, the present invention involves a compressor which makes it possible to deliver in its scattering portion an outlet flow at a given pressure from a principal flow having a first pressure and a secondary flow at a second pressure, the second pressure being greater than the first pressure, the outlet pressure being greater than the first and second pressures.
Still more precisely, the present invention involves a compressor of this type for installations for the enrichment of uranium by the gaseous scattering process. It is known that in such installations the enrichment of the gaseous mixture containing the isotopic mixture of uranium 235 and uranium 238 is done through a series of scatterers in which uranium hexafluoride circulates. In each scattering stage, i.e., in each scatterer, it is necessary both to inject the gaseous flow leaving the preceding stage and to recycle the secondary gaseous flow coming from the following stage.
The problem to be solved will be better understood by referring to the attached FIG. 1. In this FIGURE the stages N-1, N and N+1 of isotopic enrichment by gaseous scattering have been shown. The gas containing the isotopic mixture is introduced into a set of porous scattering or scatterer gates, and a fraction of this gaseous flow passes through the porous wall to be enriched in the lighter isotope, i.e., the uranium 235. This flow which has passed through the porous wall in the scatterer in row N is recycled at the inlet of the N+1 scatterer. The flow which has not scattered in the N scatterer is recycled in an upstream scatterer, the rank of which depends on the rate of enrichment. For example, in a simplified cycle, it may be considered that the principal gaseous flow which has scattered in the row N scatterer is recycled through the intermediary of a compressor in the row N+1 scatterer. In contrast, the gaseous flow which has not scattered is recycled in the row N-1 scatterer. It is therefore understood that, generally speaking, it is necessary at the inlet of each scatterer to introduce a gaseous flow mixture resulting on the one hand from the unscattered principal flow coming from the scatterer in the preceding row and on the other from the gaseous flow which has scattered and which comes from the scatterer in the lower row. In addition, these two flows, because of their passage or their nonpassage through the scattering wall, have different pressures. It is of course necessary to compress the principal flow and the derived flow to provide it with a common pressure at the outlet of the compressor compatible with the optimum operation of the installation. This is precisely the object of the present invention.
2. Description of the Prior Art
In FIG. 1, the scatterers D.sub.N-1, D.sub.N, D.sub.N+1, with gates B.sub.N-1, B.sub.N, B.sub.N+1, and compressors C.sub.N-1, C.sub.N, and C.sub.N+1 have been symbolized. The arrows represent the various recyclings of the scattered and unscattered flows.
Through French Pat. No. 1,237,157, for example, a compressor is known which allows this recycling of the secondary gaseous flow. According to this patent, the compressor includes a primary compression unit which acts on the principal flow and an auxiliary compression wheel which compresses the flow to be recycled so that the outlet flow unit has the same pressure in a so-called mixing stage. However, the conception of this stage is aerodynamically complex, and its realization is costly.